On the Method of Ovarian Ascorbic Acid Depletion as a Test for Luteinizing Hormone (LH)

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Abstract
The ovarian ascorbic acid depletion method for measuring LH activity has been studied on large series of rats from several strains. In agreement with the reports by Parlow and others, the method was found to give acceptable results using animals of Holtzman strain. The method, however, gives erratic results when using Wistar rats, apparently due to inadequate response of the ovaries of these animals when using Parlow's priming method. In Wistar rats, changing the priming procedure to 2 injections of 50 IU PMS each, 48 hr apart, followed 50 hr later by one injection of 25 IU HCG, yields, 6–9 days later, animals with ovarian weights and ascorbic acid contents of the order of those observed when using Sprague-Dawley or Holtzman rats. The sensitivity to LH (0.2 μg, LH, NIH-S1) of Wistar animals so prepared is still considerably below that reported by Parlow using Holtzman rats (0.04 μg, LH, NIH-S1). In all cases, but particularly so when one uses animals of the Wistar strain, adjustment of the ascorbic acid contents by covariance with the ovarian weights increases considerably the reliability and precision of the experiments. Using Wistar animals and, whatever the priming procedure, the covariance analysis rather than the usual mode of expressing the data as μg AA/100 mg ovary appeared as the only way of obtaining consistent results because of the considerable variations in the slope of the regression function of ascorbic acid contents/ovarian weights. Using rats of the HoltznUan strain, the covariance adjustment is still highly beneficial in regard to precision and reproducibility of the experiments.